Transpower releases independent report into events of August 9

12 October 2021

Transpower’s Chief Executive Alison Andrew has today released an independent report into the grid emergency of August 9 when insufficient generation was available to meet demand, leading to some customers being disconnected.

Ms Andrew says the organisation is committed to learning key lessons from the event and putting them into practice.

“New Zealand has not experienced an event like this since 1992 and it is our intention to avoid a repeat,” she says.

“We have contributed to the Electricity Authority’s phase one review and have accepted all recommendations made by the Authority. Work is already underway on implementation. We are also contributing to the review being led by the Ministry of Business, Innovation and Employment.”

“In addition, we commissioned our own review to help us understand the event and industry’s response on the night, to identify where we need to make changes. Our Board and Management accept the findings of that review and are committed to implementing the necessary changes.”

The review found that the root cause of the event was a shortage of generation due to the combined effect of planned generation outages, the lack of market pricing signals to incentivise the offer of available slow-start thermal generation and finally, the unexpected loss of hydro and wind generation at the peak of demand. This happened on the evening where New Zealand saw its highest electricity demand ever due to cold temperatures across the country. 

Transpower’s operational procedures, communication and error in demand allocation, exacerbated the issue resulting in some additional households losing electricity for a short period of time that evening.  The company apologises for the inconvenience that this error had on electricity consumers.  

The report also identified that Transpower’s lack of visibility over the use of controllable load by distribution networks is a barrier to the effective management of such an event.

“These issues are wider than Transpower in its role as the System Operator and avoiding a repeat of August 9 will require the commitment of the entire industry,” says Ms Andrew.

”Transpower as System Operator plays a key role in the co-ordination  of the electricity market and it is a responsibility we take very seriously.  Looking ahead success will also require active industry involvement in addressing the issues highlighted.”

“We look forward to working alongside others in the industry to makes the changes required, and demonstrate to all consumers, our collective commitment to improvement.”

“Consumers can have confidence in their electricity system which is both robust and reliable. Transpower and I am sure all industry participants are committed to avoiding a repeat of August 9.”

Transpower’s review was completed by Dr Ranil de Silva, Technical Director, PBA Consulting.

A full copy of the report including a timeline of the event, can be found here on Transpower’s website.

The Transpower Board also commissioned a review into the communications with our stakeholders surrounding the events of 9 August. Management has accepted all of the recommendations.  The report is available on our website.




For further information:

Deborah Gray, Corporate Communications Manager  

Ph: 021 624 170


Corporate Communications Team

Ph: 021 195 8613



  • Transpower is a State-owned Enterprise with dual responsibilities:
    • in its role as the Grid Owner it is responsible for developing and maintaining the high-voltage electricity transmission assets that make up the National Grid, and
    • in its role as the System Operator it is responsible for co-ordinating the electricity market system. This role is provided under contract to the Electricity Authority.

Transpower as the Grid Owner

  • Transpower coordinates more than 10,000 planned outages on the National Grid each year.
  • Unplanned outages and interruptions to transmission are trending down year-on-year, with the past financial year to 30 June 2021 showing the best performance in two decades. Over the past year Transpower recorded the lowest ever number of unplanned interruptions at 40. (Highest year FY06 recording 165)
  • Unplanned outages are categorised by cause including human error incidents, environmental, equipment, unknown and miscellaneous. Incidents caused by human error have been trending down over the long-term. Interruptions caused by equipment failure over the past decade are on average nearly half that of the previous decade in part due to the industry’s investment in maintenance and replacement.

Transpower as the System Operator

  • In its role as the System Operator, Transpower has oversight of nation-wide supply and demand. The System Operator communicates this information with market participants and the industry to enable them to make business decisions.
  • The System Operator must maintain electricity voltage and frequency within defined limits across the entire grid 24/7 in accordance with the Electricity Industry Participation Code. This is to ensure stability across the system.
  • In the event of a Grid emergency, Transpower can demand action from the industry under the Code to maintain system security. 

Events of August 9

  • On the evening of August 9 there was insufficient supply to meet demand. As a result the stability of the system was at risk. Action had to be taken to reduce demand for electricity, to prevent more wide-spread, uncontrolled outages.
  • The event, on one of the coldest nights of the year, saw around 34,000 consumers disconnected, with more than 17,000 from the Waikato impacted.